The present invention relates to a suspension device for a limb prosthesis, and to a suspension device for a limb orthosis. The invention is particularly applicable to a vacuum socket assembly for attaching a limb prosthesis to a residual limb portion. More particularly, the invention provides a new assembly and system for securing a prosthetic device to a residual lower limb portion for a transtibial amputee.
Maintaining an intimate fit between a residual body portion and the socket of a prosthetic limb is known to cause problems with the comfort and control of the limb prosthesis. It is known that these problems are, in part, due to the occurrence of relative movement between the residual body portion and the socket. Typically, this relative movement causes abrasions on the residual body portion and increased energy consumption during ambulation, as well as a lack of control of the prosthetic device.
It is known to improve amputee comfort by employing a liner made from a visco-elastic material, the liner being positioned between the residual body portion and the socket. Unfortunately, a typical liner does not breathe as it creates an airtight seal with the residual body portion in order to suspend the prosthetic device. Various methods have been devised to suspend the prosthetic device from a liner. For example, a pin attached directly to the distal surface of the liner may be fastened to the socket. Alternatively, suspension can be achieved using a flexible non-porous sleeve that is fitted externally so as to overlap the brim of the socket and to engage the wearer's skin above the socket brim thereby to create an air-tight seal.
Although the known methods can reduce relative movement of the residual body portion with respect to the prosthetic device thereby improving comfort for the amputee a further reduction is desirable.
Several innovations over recent years have sought to restrict relative movement between a residual body portion and a prosthesis further by applying an active vacuum via the liner to the residual body portion. An active vacuum is defined as one that is less than atmospheric pressure and is generated by, usually, either a mechanical or electrically powered vacuum pump. It is known to use such a vacuum pump in combination with a non-porous liner that effectively insulates and seals off air flow to the residual body portion. By ensuring an intimate fit of the liner to the residual body portion and evacuating the space between them using the vacuum pump, it is possible to secure the liner to the residual body portion purely by vacuum while minimising relative movement between the residual body portion and the liner. It is then possible to secure the liner to the socket of a prosthetic device. The Otto Bock Harmony® system is an example using this technique.
Another known liner system is the Iceross® Seal-In liner which is configured such that a vacuum is created when the residual body portion, covered by the liner, is pushed into the socket.
One difficulty encountered with all liners made of materials such as silicone is that, in a hot environment or during exertion, sweating results. This tends to increase relative movement between the residual body portion and the liner and, hence, the prosthetic device. Additionally, sweating creates a moist environment which softens the skin and provides a breeding ground for pathogens. The consequences of this are that the residual body portion is more prone to abrasion, tissue breakdown and infection. Ideally, relative motion between the skin and the socket interface should be eliminated.
It is known from WO 2007/030609 (King) to provide an inner fabric layer to act as a wicking layer between the tissue of the residual body portion and the liner. This fabric layer allows an active vacuum to propagate around the surface of the residual body portion and thereby assists in securing the liner and prosthetic device to the residual body portion. Furthermore, this wicking layer promotes the removal of fluid, i.e. sweat, from the surface of the residual body portion. Nevertheless, the potential for harbouring bacteria remains. In addition, the fabric layer can cause abrasion and damage of the tissue of the residual body portion with any relative movement.
U.S. Pat. No. 6,544,292 (Laghi) discloses a soft gel liner with a fabric-covered exterior.
EP 0182412A (Jongenengel) discloses a leather artificial limb socket having a thin flexible leather inner layer and a leather outer layer, the leather layers sandwiching therebetween a resilient thermoplastics layer bonded to the inner leather layer and having perforations which aid in the dissipation of heat and moisture from the residual limb enclosed by the socket.
U.S. 2001/0016781A (Capsers) discloses an example of a vacuum-assisted suspension socket having a flexible suspension sleeve overlapping the brim of the socket. Inside the socket, a sealed cavity is formed between the socket and a liner which is coextensive with the socket. Inside the liner is an osmotic membrane encasing the residual limb portion and, between the liner and the socket, there is a sheath of knitted nylon to aid fitting of the socket over the liner.
It is an object of this invention to provide an improved vacuum-assisted liner system and suspension device.